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PHOTOSYNTHESIS
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How do plants make their own food?
One of the raw materials that plants need to make food does come from the soil, the other comes from the air.
What are these two raw materials?
Plants use carbon dioxide and water to make their own food in a chemical reaction. What is the name of this reaction?
carbon dioxide(from the air)
water(from the soil)
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What is the name of the process?
Plants make their food from carbon dioxide and water in a chemical reaction called photosynthesis.
Oxygen gas is also made as a by-product of photosynthesis.
glucose
oxygen
carbon dioxide(from the air)
water(from the soil)
The food made by photosynthesis is the sugar, glucose.
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Where does the energy come from?
Plants need energy for photosynthesis to take place. The energy for photosynthesis comes from the Sun.
Where in a plant does photosynthesis take place?
glucose
oxygen
carbon dioxide(from the air)
water(from the soil)
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Where does photosynthesis happen?
Plant cells in the upper surface of leaves have chloroplasts which contain the green pigment called chlorophyll.
It is chlorophyll, which absorbs light energy from the Sun, that enables plants to carry out photosynthesis.
glucose
oxygen
carbon dioxide(from the air)
water(from the soil)
chlorophyll
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Photosynthesis
Plants make their own food by a process called photosynthesis.
The word equation for photosynthesis
This equation can be read as:
“Carbon dioxide and water, using light energy and chlorophyll, react to make glucose and oxygen”
light energy
chlorophyll
carbon dioxide + water oxygen+glucose
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What is needed for photosynthesis?
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What is the word equation?
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PhotosynthesisPhotosynthesisPhotosynthesisPhotosynthesis
Photosynthesis
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• Water comes from the soil
• Carbon dioxide comes from the air
• Chlorophyll is a green pigment found in the chloroplast of leaves
It traps light energy that is needed to make the glucose
chloroplast contains
chlorophyll
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The leaves are specially adapted for photosynthesis
1. Leaves are flat and thin
- To absorb maximum light
2. Leaves have tiny pores called stomata
- To allow CO2 in and O2 out
3. Leaves have chloroplasts
- These contain chlorophyll
- Chlorophyll traps light energy
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The Products of Photosynthesis
1. Glucose
• Used in respiration• Stored as starch
2. Oxygen
• Used in respiration• Released into the air
– Animals then use it for respiration
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To show that a plant produces starch
We need to show that a plant is making starch during the experiment
First we must remove any starch that is already in the plant i.e.
we must destarch the plant
To destarch a plant
It is placed in a dark cupboard for 48 hours
(The plant uses up all its stored starch and it cannot make any more)
During this experiment safety goggles must be worn!!!!!
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1. Cover some leaves with aluminium foil
(This will act as our control)
2. Place plant in strong sunlight for several hours
3. Remove leaves from plant and boil for one minute to kill them
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3. Place leaves in alcohol to remove chlorophyll
3. Now place leaves in warm water to soften
4. Place leaves on white tile and add a few drops of iodine
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Results
Iodine is a red/brown chemical
If starch is present it turns blue/black
Leaf Result Conclusion
Leaf covered in foil No colour change No starch found
Uncovered leaf Turns blue/black Starch has been made during photosynthesis
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Testing a leaf for starchTesting a leaf for starchTesting a leaf for starchTesting a leaf for starch
Testing a leaf for starch
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To show starch is produced
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The Control
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QuizQuizQuizQuiz
Quiz
Exclude Q2
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WordsearchWordsearchWordsearchWordsearch
Wordsearch
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Skool.ie lessonhttp://www.skoool.ie/content/skoool_learning/junior/lessons/science/plant_nutrition/flash/h-frame-ns6.htm
Skool.ie assessmenthttp://www.skoool.ie/content/skoool_learning/junior/assessments/science/plant_nutrition/flash/h-frame-ns6.htm
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